Leak detecting device for detecting a leak in a container

ABSTRACT

A leak detection system determines whether a container has a leak or an aperture by attempting to draw a vacuum in the container and determining whether a vacuum has been created in the container. If a vacuum can be created in a container, this indicates that the container has a leak. Conversely if a vacuum cannot be created in the container, this indicates that the container does not have a leak. The leak detection system preferably includes a conveyor system for moving a container and a sensor for sensing the pressure in the interior of the container through an opening in the top of the container. While the sensor is sensing the pressure in the interior of the container, a vacuum pump pulls air from the region around the exterior of the container. If the container has an aperture, a vacuum will be created in the container and will be noted by the sensor. Conversely, if the container does not have an aperture, a vacuum will not be created within the container and the sensor will determine this by noting that the pressure of the container is above a predetermined pressure limit. This sensor determines that the container has an aperture by noting that the vacuum in the container is greater in magnitude than a predetermined pressure limit. The leak detection system of this invention may further include a reject assembly for rejecting a container that is detected by the sensor to have an aperture and a controller for controlling the reject assembly in response to signals from the sensor.

BACKGROUND OF THE INVENTION

This invention relates to methods and systems for determining whethercontainers have apertures or leaks by trying to create a vacuum in thecontainers.

Prior art systems and methods for determining whether a container has anaperture or leak generally include a means for pressurizing a containerand a means for measuring the ability of the container to maintain apressure. More particularly, these systems and methods may includeeither a star wheel system or a conveyor system for moving containers.These systems and methods may also include a compressor or other devicefor directing the flow of a pressurized fluid into the container, and ameasuring device for measuring the pressure inside the container once itis filled with pressurized fluid. In most applications, the pressurizedfluid is air. After determining the pressure inside of the container,the measuring device typically communicates with a controller fordetermining whether the pressure of the fluid in the container exceeds apredetermined value. If the pressure of the interior of the containerexceeds a predetermined value, this indicates that the pressurized fluidhas been retained in the container and that the container does not havean aperture. Conversely, if the pressure of the inside of the containeris below the predetermined value, this indicates that the container hasan aperture or leak.

As an alternative to detecting leaks with compressed air, systems andmethods for detecting leaks in a container by determining whether acontainer can hold a vacuum have also been developed. Similar to thepressurized air systems, the vacuum type systems draw a vacuum in thecontainer and then test the ability of the container to maintain avacuum. If a container cannot hold a vacuum, this indicates that it hasa leak, and conversely if a container can hold a vacuum, this indicatesthat the container does not have a leak. Examples of such systems aredisclosed in U.S. Pat. Nos. 3,762,213 (Nowicki) and 5,025,657 (Schenk).Nowicki teaches that a vacuum can be created in a container by moving acam driven diaphragm that is attached to the top of a container that isriding on a conveyor belt. Assuming that a container does not have aleak, a vacuum is created within the container, as the diaphragm moves.If a vacuum is created in the container, the system of Nowicki raisesthe container off of the belt for a predetermined period of time andthis indicates that the container does not have a leak. However, if thesystem is unable to hold the container for the predetermined of time ina raised position, this indicates that the container cannot hold avacuum and has a leak. Similarly, Schenk teaches evacuating a containerwith a vacuum pump and then applying a pressure to the exterior of thecontainer to determine whether the container can maintain a vacuum. Ifthe container maintains a vacuum, this indicates that the container doesnot have a leak, and if the container does not maintain a vacuum thisindicates that the container does have a leak.

As described above, a variety of pressurized air and vacuum systems fordetecting the presence of a leak in a container have been developed.Many of these systems cover the top of a container with a port throughwhich pressurized air can be directed into the container or a vacuum canbe drawn in the container. Typically, this port is sealed to the top ofthe container. A pressure detector is generally placed in communicationwith the port to measure the pressure or vacuum within the container.The pressure or vacuum in the container may be measured after apredetermined period of time. This measured pressure or vacuum iscompared to a predetermined pressure that a container having no leaksshould have after it has been pressurized or depressurized for thepredetermined period of time. If the container maintains the pressure orthe vacuum for the predetermined period of time, this indicates that thecontainer does not have a leak. Conversely, if the container is unableto maintain the requisite pressure for a predetermined period of time,this indicates that the container has a leak.

This invention relates to improved systems and methods for detectingleaks in containers. This invention also relates to improved systems andmethods for detecting leaks in containers by determining if a vacuum canbe created within a container.

SUMMARY OF THE INVENTION

The leak detection system of this invention preferably determineswhether a container has a leak or an aperture by attempting to draw avacuum in the container and determining whether a vacuum has beencreated in the container. If a vacuum can be created in the container,this indicates that the container has a leak. Conversely, if a vacuumcannot be created in the container, this indicates that the containerdoes not have a leak.

Preferably, the leak detection system may be used to detect a leak in acontainer that has a first side that has an opening and a second side.It is intended that the second side of the container does not have anyapertures or leaks and that the system of this invention can be used todetect whether the second side of the container has any leaks. The firstside of the container may be the top of the container, and the secondside of the container may be the bottom of the container. Preferably,the second side of the container has a plurality of feet for supportingthe container. In order to accomplish the method of this invention, theleak detection system of this invention may have a conveyor for movingthe container, as the second side of the container rests on a belt ofthe conveyor. In addition, the leak detection system may also have asensor that has a probe, a sensor mounting block in which the sensor isdisposed, and a fluid flowing device, such as a vacuum pump, fordirecting a fluid to flow from an area around the container when theprobe is disposed proximal to the opening in the container.

In operation the conveyor moves the container to the sensor mountingblock. Once the container is disposed beneath the sensor mounting block,the probe of the sensor is placed in fluid communication with theinterior of the container. The vacuum pump pulls fluid, which ispreferably air, from the area around the container. As the vacuum pumppulls air, it is attempting to create a vacuum in the container. Avacuum in the container will be created only if the container has anaperture or leak through which air can be pulled out of the container.The sensor attached to the probe determines whether a vacuum has beencreated in the container by measuring the pressure, in the interior inthe container. If the vacuum is above the magnitude of a predeterminedpressure, this indicates that the container has a leak or an aperture.

The leak detection system may further include a reject assembly forrejecting a container that is determined to have an aperture and acontroller for controlling the reject assembly in response to thesensor. Preferably, the sensor is in electrical communication with thecontroller and causes the controller to activate the reject assembly toreject each container that is detected to have a leak.

Other features of the invention are described below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatical view of a preferred embodiment of the systemof this invention;

FIG. 2 is a cross-sectional view taken along line 2--2 of FIG. 1;

FIG. 3 is a cross-sectional view taken along line 3--3 of FIG. 2;

FIG. 4 is a cross-sectional view taken along line 4--4 of FIG. 3;

FIG. 5 is a diagrammatical view of a portion of the preferred embodimentdepicted in FIG. 1; and

FIG. 6 is a schematic diagram of a control circuit for use with theembodiment of this invention show in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1-3 illustrate a portion of a preferred embodiment of the system10 of this invention for detecting a leak or an aperture in a container12. By way of overview, the leak detection system 10 of this inventiondetects leaks in containers by attempting to create a vacuum in acontainer. In a preferred embodiment, the system 10 determines whether avacuum can be created in the containers by attempting to pull or drawair out of the interior of the container. If a vacuum can be created inthe container, this indicates that the container has a leak. Conversely,if a vacuum cannot be created in the container, this indicates that thecontainer does not have a leak.

This system may be employed with a variety of containers 12. In apreferred embodiment of this invention, the system 10 can be used todetect leaks or apertures in containers 12 that take the shape of abottle, as shown in FIG. 2, and that have a desired opening 12a on afirst side 12b, and even more preferably to plastic bottles. Thecontainer 12 with which this invention may be employed may also have asecond side 12c. The first side 12b of the container 12 may be the topof the container 12, and the second side 12c of the container may be thebottom of the container 12. The second side 12c of the container mayhave a plurality of feet 12d for supporting the container 12. In acontainer of this type, it is not intended that the container 12 has anyapertures other than the opening 12 in the first side 12b of thecontainer. Although the container 12 shown in FIG. 2 has been described,it is not intended that this invention be limited to detecting leaks incontainers of this type. Rather, it is intended that this invention beemployed to test a variety of types of containers for leaks, and thecontainer 12, shown in FIG. 2, is provided for illustrative purposes.When used with the container 12, as shown in FIG. 2, the leak detectionsystem 10 of this invention may be used to find leaks in the container12 and in particular the feet 12d of the container. Experience has shownthat the feet 12d of the container 12 are an area that is susceptible todeveloping a leak during the manufacturing process of the container.

As shown in FIGS. 1-3, the leak detection system 10 generally includes aconveying system 14, a vacuum pump 16, a probe 18, a frame assembly 19and a controller 20. In addition, the leak detection system may alsoinclude a reject assembly 22. A portion of some of these components isalso illustrated in FIGS. 4 and 5. The leak detection system 10 may beincluded within a manufacturing facility that manufacturers containersand may be used for quality control purposes to ensure that themanufactured containers do not have leaks. When employed in amanufacturing facility, the leak detection system is one system that isinvolved in the manufacturing process and may be employed following theformation of the containers.

The conveying system 14 can be used to move the containers 12.Preferably, the conveying system 14 may have a belt 24 upon which thecontainers 12 rest as the conveying system 14 moves the containers. Thebelt 24 may be moved in a rotary manner as is conventional with conveyorsystems in order to move the containers. In order to drive the belt 24,the conveying system may have rollers 26 that may be motor driven. Asthe rollers 26 rotate, the belt 24 may ride around the rollers. Althoughthe rollers 26 may be powered in a number of ways, in a preferredembodiment of this invention, the rollers 26 are motor driven. Asdescribed in more detail below, in order to detect whether thecontainers 12 resting on the belt 24 have leaks and to hold thecontainers on the belt 24, the belt 24 may have a plurality of holes 28,as best seen in FIG. 3.

A vacuum pump 16 or other suitable device, such as a blower, may bedisposed below the belt 24. In a preferred embodiment, the vacuum pump16 may be of a conventional type. In a preferred embodiment, the vacuumpump can produce a vacuum of 5-7 inches of water at about the point "A"labeled in FIG. 1. A variety of other vacuum pumps may be used with thisinvention, and it is not intended that this invention be limited to onedesign. This vacuum pump is provided for illustrative purposes and thepump ratings may vary depending on the intended application of the leakdetection system 10. As described in further detail below, the vacuumpump 16 is employed in the leak detecting system 10 of this invention toattempt to create a vacuum in a container by pulling fluid from an area17 around the container 12 and attempting to pull air out of theinterior of the container.

The frame assembly 19 may have a post 30 and a mounting block 32, asdepicted in FIG. 2. The post 30 and the mounting block 32 are preferablyformed from a metal alloy, such as a steel alloy. The post 30 ispreferably mounted to the mounting block 32 with brackets 34 and bolts36. However, the post 30 and the block 32 may be mounted together with avariety of fastening techniques including, but not limited to, usingother fasteners and welding. The post 30 forms the portion of the frameassembly 19 to which the probe 18, of the sensor 40 shown in FIG. 3, canbe mounted, so that it can interface with the opening 12a in thecontainer 12. The mounting block 32 provides the structure for mountingthe frame assembly 19 to the controller 20 and for supporting the rejectassembly 22, as shown in FIGS. 1 and 2.

The probe 18 may be coupled to a sensor 40, such as a pressure switch.Preferably, the pressure switch is a vacuum switch, which is best shownin FIGS. 3-5. In a preferred embodiment, the probe is integrallyinformed with the casing 40a of the pressure switch 40. Although anysuitable vacuum switch 40 that is suitable for the desired applicationmay be employed, in a preferred embodiment the vacuum switch 40 is aPSF-102 series pressure switch that is calibrated at 0.1 in. of water.Even more preferably, the pressure switch 40 is manufactured by WorldMagnetics of Traverse City, Michigan and is designated as part no.7162-710.

As is best shown in FIG. 2, the probe 18 and the sensor 40 may bemounted to the frame assembly 19 in a variety of manners. In a preferredembodiment, the sensor 40 is mounted to the sensor mounting block 41 ofthe frame assembly 19 with bolts 38, as best shown in FIG. 5. Preferablywhen the sensor 40 is mounted to the sensor mounting block 41, the probe18 may be disposed proximal to the path of the opening 12a in the top ofthe container 12 "follows as the container moves on the conveyor", asshown in FIGS. 2 and 3.

The probe 18 may have a hollow bore so that when the probe 18 isdisposed proximal to the path of the opening 12c of a container 12, thebore places the interior 12f of the container in fluid communicationwith the sensor 40. When in fluid communication with the interior 12f ofthe container 12, the sensor 40 can detect the pressure in the interiorof the container. The sensor 40 may be in electrical communication withthe controller 20, so that the sensor 40 can be used to determine if avacuum has been drawn in a container and communicate this to thecontroller, and described below. A wire 42 may be used to place thesensor 40 in electrical communication with the controller 20.

The sensor mounting block 41 preferably includes a casing 41a and abottom 41b that are fastened together to enclose the sensor 40. Avariety of fastening techniques may be employed to fasten the casing 41ato the bottom 41b. In the preferred embodiment shown, the casing 41a andthe bottom 41b are fastened with threaded fasteners 41c.

The bottom 41b of the mounting block 41 may have a surface 41d forcontacting a container 12, and in particular to a top of a container 12.The bottom 41b may have a first portion 41c and a second portion 41d.The first portion 41c is preferably substantially parallel to theconveyor, and the second portion 41d is preferably tapered (disposed atan angle to the first portion) with respect to the first portion. Thesecond portion 41d is preferably disposed proximal to the direction ofmotion of the containers on the belt. The probe 18 extends through anopening 41e in the sensor mounting block 41 and through the firstportion 41c of the sensor mounting block 41.

In order to test the container for leaks, the sensor 40 may sense thepressure in the interior 12f of the container 12 and compare thepressure of the interior 12f of the container to a predeterminedpressure limit. If the pressure is greater in magnitude than apredetermined pressure limit, this indicates that the container has aleak. Even more specifically, if the sensor senses that the containerhas a vacuum that is greater than a predetermined pressure or vacuumlimit, this indicates that the container has a leak.

In further detail, testing the container 12 for leaks includes placingthe second side of the container on the belt 24 of the conveyor system.The belt 24 moves the opening in the top of container 12 into proximitywith the sensor mounting block 41. As the belt 24 is moving, the vacuumpump 16 disposed below the belt is operating. As the container is movingon the conveyor, the vacuum pump 16 holds the container 12 upright onthe belt 24 by creating a negative pressure proximal to the belt pullingfluid, or air, through the holes in the conveyor belt 24 and from thearea 17 around the container 12. When the container 12 reaches thesecond portion 41d of the sensor mounting block 41, the container slidesbelow the second portion 41d, as best understood with reference to FIG.3. The top of the container contacts the sensor mounting block 41 andslides below the first portion 41c of the bottom 41b sensor mountingblock 41. Depending on manufacturing tolerances, the top of thecontainer may contact either the first portion 41c or the second portion41d of the sensor mounting block 41. Because the second portion 41d ofthe sensor mounting block 41 is tapered, it functions to slide thecontainer 12 below the first portion 41c of the sensor mounting block41. This is of particular importance when containers are slightlylarger, because without this tapered second portion 41d, there is thepotential that a slightly large container could contact the side of thesensor mounting block 41 and be toppled over rather than movingunderneath the first portion of the sensor mounting block 41.

When the container 12 is under the first portion 41c of the sensormounting block 41, a semi-seal is created between the first portion 41cand the top of the container 12. The seal is not a perfect seal, and thequality of the seal depends on manufacturing tolerances. The seal issufficient so that a vaccum can be drawn in the container if it has aleak.

While the conveyor system is operating, the vacuum pump pulls fluid fromthe area 17 around the container 12. As the container 12 passes belowthe probe 18 as shown in FIG. 3, the sensor 40 senses the pressure ofthe inside of the container 12 and compares its magnitude to thepredetermined pressure limit. If the container does not have a leak, thevacuum pump 16 will not pull air out of the container and a vacuum willnot be created.

However, if the container 12 does have a leak, the vacuum pump 16 willpull air from the interior 12f of the container 12 and create a vacuumin the interior 12f of the container 12, as best shown in FIG. 3. Thesensor 40 will sense that the pressure in the container 12 is greater inmagnitude than the predetermined pressure limit. This indicates that thecontainer has a leak. Thus, the system of this invention can determineif a container has a leak by trying to draw air out of a container andby determining whether a vacuum can be created or drawn in the container12.

Since the vacuum pump 16 is pulling air from the second side of thecontainer 12, which is in this instance the bottom of the container, thesystem of this invention is particularly aimed at detecting leaks in thebottom of the container, which may have a plurality of feet. However,the container 12 could be of another type that has multiple openingsthat are covered while a vacuum is attempted to be created in thecontainer. Furthermore, the system of this invention could employ aplurality of vacuum pumps 16 that pull air from a variety of directionsand thereby test each side of the container for leaks.

As alluded to above, the leak detection system 10 of this invention mayalso have a reject assembly 22 and a controller 20. As is best shown inFIG. 2, the reject assembly may include a pair of cylinders 44, 46, ablock 48, a reject valve 50 and a rod 52. The rod 52 is preferably analloy metal rod, such as a steel alloy. The rod 52 may be attached tothe block 48, which is preferably an extruded metal alloy block, by anyone of a number of known fastening techniques. In the embodiment shown,the rod 52 is attached to the block 48 with screws 54. The block 48 maybe attached to the mounting block 22 of the frame assembly 19 in any oneof a variety of manners, including by fastening the block 22 withthreaded fasteners 56.

Each of the cylinders 44, 46 preferably has a clamping end 58 thatdefines a clamp. A bolt 60 may be employed to clamp the end 58 of eachcylinder 44, 46 about the rod 52. The cylinders 44, 46 are preferablyclamped on the rod 52 at a height so that they can reject a container 12that is detected to have a leak.

Each of the cylinders 44, 46 may have a piston 65 that is moveableinside of the cylinders 44, 46 and that can be moved, as showed indashed lines in FIG. 2 in order to reject a container 12 by pushing itoff of the conveyor belt 24. The pistons 65 are preferably pressurizedor spring loaded to a first position and moveable to a second positionin which they extend from the cylinders 44, 46 and move the eject pad 64disposed on their ends to contact a container 12 and reject it. Theeject pads 64 are preferably manufactured from aluminum. The eject pad64 is also best seen in FIG. 2.

Preferably, the pistons 65 move in response to the supply and venting ofa pressurized fluid, which may be air. In order to move the pistons 65from their first position to their second positions, pressurized air isported to one side of the piston 65. This causes the pistons 65 to moveto reject a container 12. In order to move the pistons 65 back to theirfirst positions, the pressurized air is vented from the pistons 65 andthe pressure on the other side of the piston causes it to return to itsfirst position.

In order to control the operation of the cylinders 44, 46, the rejectassembly may have a reject valve 50. Preferably, the reject valve 50 isa three way valve that may be connected to the cylinders 44. The threeway valve 50 is preferably a solenoid operated valve that is operated bythe controller 20 as described below. The solenoid valve may be a 1/8in. NPT 3-way valve manufactured by MAC and having the designation ofpart no. 111-CA. As shown in FIG. 2, the three way valve has three ports50a, 50b, 50c. Two of the ports 50a, 50b are connected to conduits 66,which may be polyvinyl tubing. Another of the ports 50c is connected tothe lower cylinder 44. The port 50a may be connected to the tubing thatsupplies pressurized air from an air source, for example a compressor(not shown), to the reject valve 50.

As described below, the operation of the reject valve 50 is controlledby the controller 20. In a first position, the reject valve 50 is in avent position in which the supply port 50a is shut and pressurized aircan not travel through the reject valve 50 to the pistons 65. In thisposition, the reject valve 50 is vented to atmosphere. When a containerthat has a leak is detected by the sensor 40, the controller 20 willcause the reject valve to be repositioned. When this occurs, the rejectvalve 50 repositions so that the supply port 50a is opened to place theports 50b and 50c and a side of both of the pistons in fluidcommunication with the supply tubing. In this position, pressurized airis directed to a side of the pistons to cause the pistons 65 toreposition and reject the container as described above. After thecontainer with the leak has been rejected, the controller 20 causes thereject valve 50 to reposition and back to its vent position and removethe sides of the pistons from being in fluid communication with the airsupply. When the reject valve 50 repositions, the side of the pistonsthat had been pressurized is vented to atmosphere and this causes thepistons 65 to move back to their normally retracted position.

The controller 20 may include a housing 68 and a control circuit 70 forcontrolling the operation of the reject assembly 22 based upon inputsfrom the sensor 40. The housing 68 is preferably connected to themounting block 32 of the frame assembly 19 by any one of a variety ofconventional fastening techniques. The housing 68 houses the controlcircuit 70, which preferably uses 110 VAC electrical power from a powersource 71. As shown in FIG. 6, the control circuit 70 generally includesa power on switch 72, a test switch 74, a sensor or pressure switchcontact 76, a control relay 78, a first time delay contact 80, a firstcontrol contact 82, a second control contact 84, a time delay relay 86and a reject valve relay 88. These components are preferablyelectrically connected as shown in FIG. 6. However, they may beconnected in a variety of ways that will result in the control of thereject assembly 22 in response to the sensor 40. Each of the contactsshown in FIG. 6 is shown in its deenergized state.

The purpose of the control circuit 70 is to control the operation of thereject assembly 22, and in particular the reject valve 50, in responseto signals from the sensor 40. As described above, the sensor 40 sensesthe pressure in the interior of the container and compares the magnitudeof the pressure to a predetermined pressure limit to determine if avacuum, that is indicative of a leak, is present in the container. Thesensor 40 is in electrical communication with the pressure switchcontact 76, so that the pressure switch contact 76 shuts and opens inresponse to signals from the sensor 40. If the sensor 40 senses that thepressure limit in the interior of the container is indicative of a leak,the sensor 40 sends a signal to the pressure switch contact 76 to causethe pressure switch contact to close. Although not described above, thesensor 40 also detects when the pressure exceeds a predetermined resetpressure that is indicative of the sensor 40 not sensing a vacuum withina container. Thus, after the sensor 40 senses a vacuum in a containerand sends a signal to cause the pressure switch contact 76 to close, thesensor determines when the pressure has exceeded the predetermined resetpressure limit and at this point causes the pressure switch contact 76to move back to its open state. As described below, when the pressureswitch contact 76 moves to its closed position, this causes the rejectassembly 22, and in particular the reject valve 40 to be operated toreject the leaky container that has been detected. In a preferredembodiment of this invention, the predetermined limit at which thesensor 40 sends a signal to the pressure switch contact 76 to move tothe closed position is about 0.1 inches of water, and the predeterminedreset pressure limit at which the sensor 40 sends a signal to thepressure switch contact 76 to move to the open position is less than thepredetermined limit that causes the pressures with contact 76 to close.Preferably, these limits or set points are adjustable with an adjustingscrew 89 or the like disposed on the sensor 40.

Both of the control contacts, the first and the second control contacts82, 84, are in electrical communication with the control relay 78, sothat the control relay 78 controls whether they are in the open orclosed position. Similarly, the time delay relay 86 controls theoperation of the first time delay contact 80.

As shown, the test switch 74 is placed in parallel with both thepressure switch contact 76 and the first control contact 82 and thefirst time delay contact 80. The test switch 74, the pressure switchcontact 76 and the combination of the first control contact 82 and thefirst time delay contact 80 are connected in parallel with the controlrelay 78 to control when the control relay 78 is energized. The secondcontrol contact 84 is connected in series with the time delay relay 86and the reject valve relay 88, which are connected in parallel.

In operation the power switch 72 can be moved from an off position to anon position in which it supplies electrical power from the power source71 to the control circuit 70. The control relay 78 will be energizedwhen either of the following two events occur, either the test switch isactivated or the pressure switch contact 76 is shut in response to asignal from the sensor 40, as described above. Thus, if the sensor 40detects a vacuum in the container that is equal to or greater than thepredetermined pressure limit, the pressure switch contact 76 will moveto the closed position. After the pressure switch contact 76 closes,electrical power is supplied from the power source 71 through thepressure switch contact 76 to energize the control relay 78. Onceenergized, the control relay 78 causes the first control contact 82 andthe second control contact 84 to move to their closed positions. In itsclosed position, the first control contact 82 enables power to besupplied from the power source 71 through the first control contact 82and the normally shut first time delay contact 80 to energize thecontrol relay 78. This keeps the control relay 78 powered after thepressure switch contact 76 opens upon receiving an opening signal fromthe sensor 40 when the predetermined reset limit is reached.

When the control relay 78 is energized as described above, the controlrelay 78 causes the second control contact 84 to move from its openposition to its closed position. In its closed position, the secondcontrol contact provides electrical power form the power source 71 tothe time delay relay 86 and the reject valve relay 88. By energizing thereject valve relay 88, the reject valve 50 changes position to cause thereject assembly 22 to reject a container 12. The rejected container isone that the sensor 40 has detected that has a vacuum that is above thepredetermined pressure set point or limit.

When energized, the time delay relay 86 causes the first time delayrelay 86 contact to move from its normally closed position to its openposition. Because of the time delay associated with the time delay relay86, the time delay relay 86 generally causes the first time delay relaycontact 80 to move to the open position after a predetermined timedelay. In a preferred embodiment of this invention, the time delay isabout 0.1 seconds. The time delay provided for by the time delay relay86 ensures that the control relay 78 will be powered long enough toprovide power to the reject valve relay 88 and power the reject valverelay 88, so that the reject valve relay 88 can operate the reject valve50.

After the first time delay contact 80 opens, electrical power is removedfrom the control relay 78 and its associated contacts, the first 82 andthe second control contact 84 move to their normally opened position.When the second control contact 84 moves to its opened position, poweris removed from the time delay relay 86 and the reject valve relay 88.By removing power from the reject valve relay 88, the reject valvesolenoid is deenergized and the reject valve 50 moves to its initialposition. When the time delay relay 86 is deenergized, the first timedelay contact 80 shuts, so that it it ready to energize the controlrelay 78 when the sensor 40 detects the next container that has apressure above the predetermine pressure limit.

In summary, the control circuit operates to control the reject valve 50in response to the sensor 40. The sensor 40 ends a signal to the controlcircuit 70 when it detects a container 12 that has a vacuum that isgreater than a predetermined limit or set point. This signal causes thecontrol circuit 70 to power the reject valve 50 and thereby reject thecontainer that had the leak. After the sensor 40 is disconnected fromthe leaky container and the magnitude of the pressure detected by thesensor 40 is less than or equal to a predetermined reset point, thecontrol circuit 70 is reset so that it is ready to receive the nextsignal from the sensor 40 when it detects a leak in another container12.

As shown in FIG. 6, the control circuit 70 may also have a power activelight 90 that is powered when the power switch 72 is set to the onposition. Further, the controller 20 may also have a counter circuit 92that energizes a counter 94 that counts each container 12 that isrejected. A preferred embodiment of this counting circuit 92 is shown inFIG. 6 and includes a second time delay contact 96, a test button 98,and the counter 94. The counter 94 may be one of a variety of typesincluding but not limited to an electrical mechanical counter or anelectrical counter with an LED display. In a preferred embodiment, thecounter 94 is one that is manufactured by Red Lion Controls of York, Pa.and is either a Cub 1 miniature electronic counter or a Cub 2 generalpurpose counter. As shown, in FIG. 6, the second time delay relaycontact 96 is normally open. When the time delay relay 86 is energized,as described above, the second time delay contact 94 will shut and powerwill be provided to the counter 94 for amount of time sufficient tocause the counter 94 to count one unit.

As described above, the leak detection system 10 of this inventiondetects leaks in a container 12 and then rejects the container 12 if itdetects the presence of an aperture or leak in the container 12. Inorder to accomplish this, the leak detection system 10 10 has a probe 18that it coupled to a sensor 40 and mounted in a sensor mounting block41. As a container 12 moves on the conveyor belt, the container 12 willreach the sensor mounting block 41 and becomes disposed below the probe18. Once disposed below the probe 18, the interior of the container isin fluid communication with the sensor 40. The vacuum pump draws fluidfrom the area 17 around the container 12. Thus, if the container 12 hasan aperture, the vacuum pump will draw air out of the interior of thecontainer 12 and a vacuum will be created in the container 12. If avacuum is created in the container, the sensor 40 will sense the vacuumbeing above the predetermined pressure limit and activate the controller20 and in particular the pressure switch contact 76 of the controlcircuit 70. The controller 20 will respond to the sensor 40 byactivating the reject assembly 22, as described above by activating thereject valve solenoid, to reject the container 12. In contrast, if thevacuum pump is unable to create a vacuum in the container 12, thisindicates that the container 12 does not have a leak and the sensor 40does not activate the controller 20 to activate the reject assembly 22.

Since the leak detection system 10 of this invention determines whethera container has a leak by attempting to draw a vacuum in the containerby drawing air from the bottom of the container 12, it is most useful indetermining whether a container has a leak or aperture in the bottom ofthe container or the direction in which the air is pulled. In apreferred embodiment of this invention, it is used with containers thathave feet and is employed to determine if the container has a leak inthe feet of the container.

It is to be understood, however, that even in numerous characteristicsand advantages of the present invention have been set forth in theforegoing description, together with details of the structure andfunction of the invention, the disclosure is illustrative only, andchanges may be made to detail, especially in matters of shape, size andarrangement of parts within the principles of the invention to the fullextent indicated by the broad general meaning of the terms in which theappended claims are expressed.

What is claimed:
 1. A system for detecting the presence of an unwantedaperture in a container that has an opening comprising:a continuouslymoving air permeable conveyor for moving the container such that thecontainer opening moves along a path; a vacuum source in fluidcommunication with the conveyor for creating a negative pressureproximal to the air permeable conveyor; and a pressure sensor, mountedproximal to the path of the container opening so that the sensor isplaced in fluid communication with the container opening as thecontainer opening moves along the path, said sensor being operative todetect a pressure decrease within the moving container if the vacuumsource pulls air through said unwanted aperture when the conveyor movesthe container proximal to the sensor, thereby determining if thecontainer has an unwanted aperture by determining the pressure decreasein the container.
 2. The system of claim 1, wherein the pressure sensorfurther comprises a probe that has a hollow bore that places the sensorin fluid communication with the container opening as the conveyor movesthe container along the path.
 3. The system of claim 1, wherein theconveyor comprises an air permeable belt.
 4. The system of claim 3,wherein the vacuum source is disposed beneath the air permeable belt. 5.The system of claim 1, further comprising a reject assembly that iscoupled to the pressure sensor and that is operative to reject thecontainer if the sensor detects the pressure decrease.
 6. The system ofclaim 5, further comprising a controller, coupled to the pressure sensorand the reject assembly, that is operative to control the rejectassembly in response to the sensor.
 7. The system of claim 1, whereinthe container has a bottom comprising a plurality of feet.
 8. The systemof claim 1, further comprising a stationary sensor mounting block inwhich the sensor is disposed and wherein the conveyor moves thecontainer so that the opening of the container moves beneath the sensormounting block while moving on the conveyor.
 9. The system of claim 8,wherein the sensor mounting block comprises a probe that places thepressure sensor in fluid communication with an interior of the containerthrough the opening in the container when the container passes beneaththe sensor.
 10. A system for detecting the presence of an unwantedaperture in a container that has a top that has a desired opening and abottom, comprising:a continuously moving conveyor that is operative tocontinuously move the container so that the desired opening moves alonga path, the conveyor comprising a continuously moving belt that has anair permeable surface for supporting the bottom of the container; astationary pressure sensor, mounted proximal to the path of the desiredopening, the pressure sensor being placed in fluid communication withthe desired opening as the opening passes proximal to the sensor and ifthe container has the unwanted aperture, the pressure sensor beingoperative to detect a decrease in pressure within the container when thesensor is placed in fluid communication with the desired opening andwhile the container is moving; and a vacuum source, disposed in fluidcommunication with the air permeable surface and (i) being operative tocreate a negative pressure proximal to the air permeable surface andproximal to the container as the belt and the container pass proximal tothe sensor and as the opening is placed in fluid communication with thepressure sensor and (ii) if the container has the unwanted aperture,being operative to pull air from within the container and through theunwanted aperture to create a decrease in pressure inside of thecontainer that can be detected by the pressure sensor, when thecontainer is placed in fluid communication with the pressure sensor andas the container is moving thereby determining if the container has anunwanted aperture by determining the pressure decrease in the container.11. The system of claim 10, wherein the vacuum source comprises a vacuumpump.
 12. The system of claim 10, wherein the belt comprises a pluralityof holes that define the air permeable surface and through which thevacuum source pulls air to create a negative pressure proximal to theair permeable surface.
 13. The system of claim 12, wherein the vacuumsource comprises a vacuum pump that is disposed beneath the airpermeable surface.
 14. The system of claim 10, wherein the sensorcomprises a vacuum switch.
 15. The system of claim 10, furthercomprising a reject assembly, that is coupled to the sensor, and that isoperative to reject the container in response to the sensor if thesensor detects the pressure decrease.
 16. The system of claim 15,further comprising a controller, that is coupled to the pressure sensorand the reject assembly, the controller being operative to control thereject assembly in response to the sensor.
 17. A method of detecting thepresence of an unwanted aperture in a container that has an opening,comprising:disposing the container on a continuously moving airpermeable surface of a conveyor; continuously moving the conveyor sothat the opening passes proximal to a stationary pressure sensor, theopening being placed in fluid communication with the sensor as thecontainer passes proximal to the pressure sensor; pulling air with avacuum source through the air permeable surface while the containerpasses proximal to the sensor, and if the container has the unwantedaperture, pulling air from within the container and through the unwantedaperture and thereby causing a decrease in pressure within the containerwhile the sensor is in fluid communication with the container; andsensing a pressure within the container when the container is placed influid communication with the sensor and while the air permeable surfaceis continuously moving and if the container has the unwanted aperturedetecting the decrease in pressure created by the vacuum source when theconveyor moves the container proximal to the sensor, thereby determiningif the container has an unwanted aperture by determining the pressuredecrease in the container.
 18. The method of claim 15, wherein thevacuum source comprises a vacuum pump.
 19. The method of claim 17,wherein the step of continuously moving further comprises moving the airpermeable surface so that the container is disposed beneath a sensormounting block in which the sensor is disposed.
 20. The method of claim17, further comprising the step of rejecting the container if thecontainer is determined to have the unwanted aperture by activating areject assembly, that is coupled to the pressure sensor, the rejectassembly being operative to contact the container and knock thecontainer off of the air permeable surface in response to the pressuresensor detecting the decrease in pressure.
 21. The method of claim 20,wherein the step of sensing comprises sensing the pressure with a sensorthat is in communication with a controller that controls the rejectassembly to reject the container if the sensor detects the decrease inpressure within the container.